The present invention relates to a backlight unit and a display device having a backlight unit.
Transmission-type liquid-crystal display devices are display devices designed to display an image by applying a voltage to liquid crystals to change orientation thereof to thereby selectively transmit light.
In many such devices, a backlight unit for generating transmitted light is provided on the back face of a liquid crystal display.
A backlight unit typically has a light source for emitting light and a light-guide plate for guiding the light emitted by the light source to a display device.
When such a backlight unit is provided, however, the light source or the shielding material thereof will be deteriorated by the usage thereof, and such deterioration may change the optical characteristics of transmitted light, resulting in deterioration of the display quality.
If this is the case, the optical characteristics of transmitted light must be controlled to improve the display quality. It is thus desirable to provide units for detecting the optical characteristics of the transmitted light to obtain information required for the control.
It has therefore been proposed to provide an optical sensor to face a light-guide plate, so that the optical characteristics of light transmitted by the light-guide plate are detected to control the optical characteristics of light emitted by the light source.
The optical sensor need be arranged at a position not blocking the transmitted light directed to the display device.
A configuration satisfying these requirements is disclosed in Japanese Laid-Open Patent Publication No. 2005-70065 (Patent Document 1), in which a dimension of a light-guide plate is extended to be greater than a display area and a photo detector (optical sensor) is provided to face the extended portion.
Specifically, FIG. 9A depicts a display device 51 in which a dimension of a light-guide plate 57 is extended to be greater than a display area 55 of a display panel 53.
An optical sensor 59 is provided to face the extended portion.
According to this configuration, the optical sensor 59 is arranged at a position not blocking transmitted light emitted by a light source 61.
Further, Japanese Laid-Open Patent Publication No. 2007-18846 (Patent Document 2) describes a configuration in which an optical sensor is arranged to face a side of a light-guide plate.
Specifically, FIG. 9B depicts a backlight unit 71 in which an optical sensor 75 and a light source 77 are arranged to face the side of a light-guide plate 73.
According to this configuration, the optical sensor 75 is arranged at a position not blocking transmitted light emitted by the light source 77.